A CMOS image sensor has image-sensing elements configured to acquire an image signal from a subject and a logic circuit configured to perform an image processing operation that can be incorporated on the same chip by use of the same manufacturing process. This is effective in providing a compact structure. However, in the CMOS image sensor, the mean pitches of circuit patterns in an image-sensing element region and logic circuit region are different in the order of digits. Due to this, a problem that the quality of the image-sensing element is degraded tends to occur.
That is, since the mean pitches of the circuit patterns in the respective regions are greatly different, it is predicted that the temperature of the logic circuit region becomes higher than that of the image-sensing element region in an optical annealing process that is one of the manufacturing processes. This is because the pitch of gate conductors (GCs), which are circuit patterns of the logic circuit, is smaller than the incident wavelength and the light absorption rate becomes higher in comparison with that in the image-sensing element region.
If the temperature of the logic circuit region becomes higher than that of the image-sensing element region, heat transfers from the logic circuit region to the image-sensing element region due to thermal diffusion in a portion of the image-sensing element region that is close to the logic circuit region. As a result, temperature irregularities occur in the peripheral region of the image-sensing element region. Such temperature irregularities cause a variation in the characteristic of each image-sensing element and lead to degradation in the quality.